The present invention generally relates to luminaires for illuminating a space, and more particularly to luminaires for lighting a confined space.
With ever increasing energy costs and the push to reduce energy consumption, building owners are under pressure to reduce the amount of energy devoted to lighting. Reduction in energy consumption for lighting can be achieved by replacing inefficient light sources with light sources that consume less energy for a given light output. Reduction in energy consumption is also often achieved by simply turning down the lights to thereby reduce the amount of ambient lighting in the room, and supplementing light on work surfaces, such as table tops and desk tops, in work spaces with task lighting, such as desk lamps or under-counter lights. Because task lights do not need to generate the amount of light needed to illuminate an entire room, they consume far less energy. From an energy efficiency point of view, only task lights would be used in a space, without ambient lighting. However, from a practical point of view some ambient lighting is required for circulation and to provide visibility to surrounding architectural structures and amenities in the space. For example, if the ambient lighting in a task lit space were reduced from 30 footcandles to 10 footcandles, the energy savings would be substantial.
The problem with relying on task lighting in a space with a low level of ambient lighting is that the areas immediately surrounding the task surfaces will not be well lit. The task lighting will permit a person working at the task to see his or her task without difficulty, but colleagues stand or sitting in proximity to that person will be in low light and shadows, making personal interactions more difficult and the overall work environment less inviting.
The present invention overcomes the problem of providing well-lighted working spaces in a low ambient lighting environment. The invention provides a luminaire and method for illuminating a task surface as well as illuminating a localized volume of space above and about the task surface (sometimes referred to herein as “surround volume”) without a significant contribution from low ambient lighting. The luminaire and method of the invention provide vertical illumination at and in proximity to the task surface sufficient to illuminate features, such as facial features, within the surround volume and does so in a manner that avoids harsh highlights and/or shadows on such features. In its illustrated embodiment, the invention also addresses the problem of providing volumetric illumination in a manner that does not create visual discomfort caused by light sources exhibiting excessive brightness.